Add CSS handbook (#10941)

books/free-programming-books-langs.md

@@ -952,6 +952,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Code Guide: Standards for developing flexible, durable, and sustainable HTML and CSS](http://mdo.github.io/code-guide/) - Mark Otto
 * [CSS Animation 101](https://github.com/cssanimation/css-animation-101)
 * [CSS Notes for Professionals](http://goalkicker.com/CSSBook) - Compiled from StackOverflow Documentation (PDF)
+* [CSS Transition vs CSS animation](https://www.freecodecamp.org/news/css-transition-vs-css-animation-handbook/) - Oluwatobi Sofela
 * [Dive Into HTML5](http://diveinto.html5doctor.com) - Mark Pilgrim ([PDF](http://mislav.net/2011/10/dive-into-html5/))
 * [DOM Enlightenment](http://domenlightenment.com) - Cody Lindley (HTML)
 * [Essential CSS](https://www.programming-books.io/essential/css/) - Krzysztof Kowalczyk, StackOverflow Contributors